Pulverization



M. FRISCH PULVERIZATION Feb. 4, 1936 Filed March 30, 1952 m M m o Mm Z QM v N E Patented Feb. 4, 1936 UNITED STATES PATENT OFFICE PULVERIZATION Martin Frlsch, New York, N. r., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application March 30, 1932, Serial No. 601,915

Claims. (Cl. 83-9) My invention relates to pulverizing mills and from any suitable feeder by means of the conmore particularly to classifiers used with air-,- duit I1 and chute H. The air employed in swept mills for separating and returning relasweeping the pulverized material from the mill tively coarse material to the mill. Still more enters through conduit l8 and passes through a 5 particularly, my invention relates to classificareceptacle is associated with the hollow [rum 5 tion in connection with mills of the ball type. nion l2. An adjustable slide door or valve The primary object of my invention is to promember 20 may be opened to supply additional vide a classifier for effectively and regulatably air for sweeping the mill when desirable. separating the relatively coarse particles of ma- Extending into the hollow trunnion ii is the terial drawn from the mill by a current of air, inlet connection 2! to the classifier casing 22. 10 and to provide means for returning the sepa- Casing 22 of the classifier is supported by rated coarse material directly to the mill for furbrackets 23 and 24 bolted to the foundation 25. ther pulverization. A conduit 26 is connected to a suction fan F The usual arrangement of a suction fan befrom whichth'e mixture of air and pulverized l5 tween a ball mill and a classifier mounted above material is fed directly to a furnace or conducted the mill is unsatisfactory because the coarse to a separator of a storage system, as desired. particles entering the fan will rapidly wear out In the upper central portion of the casing 22 of the fan blades. On the other hand if the sucthe classifier is the deflecting p t or baffle 21 tion fan is placed beyond the classifier and the which may be adjusted from the outside by classifier is remote from the mill, the conduit means of the wing nut 28. In the lower central 20 between the classifier and mill is likely to beportion of the classifier is the stationary curved come obstructed to some extent by coarse parbaflle 29 and associated therewith is a curved deticles that are too heavy to befioated to the fleeting plate 30 guided close to plate 29 and classifier and returned by gravity to the mill. which may be adjusted by rotating shaft 3! hav- It is a further object of my invention to overing levers 32 mounted thereon, to which plate 25 come the above difficulties by locating the classiis attached. An external hand lever 42 and fier directly at the outlet of the pulverizing mill clamping nut 43 are provided to rotate shaft 3| so that the coarse particles or oversize do not and fix the position of baflle 30. The arrows inreach the suction fan and cannot obstruct the dicate the path of the mixture over the bailles 30 passage of the finely pulverized material on its and deflecting plates which may be generally 30 way to a point of use or storage. This is of pardescribed as being in the form of an S. ticular advantage in connection with ball mills, A screw conveyer 33 arranged in trough 33' as will be clear from the following description. is driven through gears 34 and 35 by means of My novel combination of classifier and ball mill a universal shaft coupling 36 and spider connec- 35 provides a simpler and more efilcient apparatus tion 31 attached to the rotating casing IS. The 35 than previously known arrangements of similar gears 34 and 35 are covered by a housing 38. k A wire screen 39 of large mesh is arranged to Other objects and advantages of my invention cover the screw conveyer and extends from baffle will be apparent from the following detailed de- 29 to the outlet 40 of the screw conveyer. The

40 scription of preferred embodiments thereof as mesh of screen 33 is large enough, say inch, illustrated in the, accompanying drawing, of to permit coarse particles to pass downwardly which: v therethrough onto the screw conveyer while pre- Fig. 1 is a vertical cross-sectional view of a venting the passage therethrough of grinding ball mill and classifier embodying the invention; ball or large tick of w od,

46 Fig, 2 is a cross-sectional view of the classifier, The modificatio sho i Fig, 3 i simila to taken on line 22 of Fig. 1; and the construction shown by Fig. 1 except that the Fig. 3 is a vertical cross-sectional view showarrangement of deflecting plates is diiferent. A ing a modified classifier construction. fiat ballie ll extends in a slanting direction The ball m ll in is p v d d at ea h nd wit across the chamber formed by casing 22. At the 50 hollow trunnions H and I2 which are journalled top of the chamber is the deflecting plate 42 50 in the supporting brackets 53 and H. The mill which may be adjusted to difierentpositions. is rotated by the ring gear l5 mounted upon the The operation of the apparatus is as follows: cone-shaped portion of the casing it of the ball Material to be pulverized, which in the present mill. case may be coal, is fed to the mill through chute 55 The material to be pulverized is fed to the H." to the rotating hollow trunnion l2 into the 55 presence of grinding .balls within the rotatable drum. llhe fan F is employed to draw a current of air through the mill and classifier. Control of air flow is in general controlled by a by-pass valve for air to the fan F and the valve 20. The member 21 may also be used to control the air flow by moving the same over the inlet opening of conduit 26. The velocity of the air flow through the mill is such that the fines are removed as soon as formed, thusgiving a maximum amount of finely pulverized coal with a minimum power consumption. The classifier is preferably of large volume, for example at least of the volume of the mill proper and the fan is preferably operated to carry a relatively large proportion of coarse material out of the rotating drum into the classifier. The classifier is so constructed that it is able to handle a very large quantity of oversize material. The main separation of the fines and oversize occurs in the chamber to the right of the bafie 29. The speed of the air flow through the classifier determines to a large extent the amount of oversize dropped by the moving stream of air and coal. The deflecting plates 2? and are provided for the purpose of regulating the velocity of the air flow through the classifier by changing the length of the path over which the material passes. Assume for the purpose of illustration that deflecting plate 21 is swung to the extreme left hand position and that deflecting plate 30 is moved to its extreme right hand position. With the position of the deflecting plates as just indicated, it will be seen that a substantially 85 straight line of flow through the classifier will be provided and that little or no separation of the oversize particles of coal will occur in the chamber to the right 01' baiile 29 since the direction of the moving stream has not been substantially altered. Now considering the deflecting plates as indicated in Fig. 1 of the drawing, it is clear that the direction of the air stream as well as the heavy oversize particles will be changed, and that due to this abrupt change of direction, especially in the last pass of the air and coal through the classifier, considerable, it not all, oversize will be dropped and conveyed by the screw conveyer to the mill for further treatment. The heavier particles being given a downward direction of flow, in the large chamber where the air velocity is relatively low, they will not be carried around plate- 2'! but will continue downwardly to the screw conveyer whereas the air stream will carry the lighter particles along to the fan. It will be seen that gravity assists in the classification. I

The screw conveyer is rotated at a speed considerably higher than that of the mill because of the difierences in diameter of gears 36 and 35-;

The operation of the modified form of classifier shown in Fig. 3 is similar to that shown in Fig. 1 but is of simplified construction as regards the arrangement of baiiie and deflecting plate in the first pass. a

It will be seen that by controlling the position of the classifier plates, practically any degree of classification can be obtained. Furthermore the classifier plates vary the air flow. With the position of plate 30 shown in Fig. 1, the air is first I veyer.

The positioning of the large classifier immediately adjacent the outlet of the mill permits return of a large amount of coarse material without conveying the same any considerable distance and also takes care of overflow of balls.

It will be understod that various changes in structure may be employed without departing from the spirit or scope of the invention; Suitable access doors may be provided in the wall of the classifier and other auxiliary devices willbe apparent to those skilled in the art.

Having thus describedmy invention, what I claim is: v

1. Pulverizing apparatus comprising a rotatable drum having an end trunnion providing an outlet for the drum, a classifier having an inlet member associated with said trunnion, means for withdrawing fluid from said classifier, a screw conveyor in said classifier and extending within said trunnion, a baflle providing a plurality of vertical passages in said classifier, said conveyor being situated at the bottom of said passages, and

a screen at the bottom of one of said passages the casing providing a plurality of vertical passages between the inlet and the outlet, a screw conveyor having a diameter approximately the same as that of said circular portion located in and confined to the lower part or said trough so that the upper part of the trough is unobstructed thereby, a drive shaft extending from within said mill through the upper part of said trough, the end of said shaft within said mill being connected thereto so as to be rotated thereby, and means connected to the other end of said shaft for transmitting rotational movement to said screw conveyor at an increased speed of rotation.

3. Pulverizing apparatus comprising a drum having an inlet and an outlet, means'for introducing material to be pulverized into the drum. a classifier having an inlet connected to the outlet of the drum, means for withdrawim pulverized material from the drum and through the classifier, a bafiie in the classifier for directing the flow of pulverized material therethrough, means for adjusting the baflle so as to vary the path of flow of the pulverized material through the classifier, means for returning coarse material from the classifier to the drum, and a screen at the bottom of the baille and above said last mentioned means and disposed between the baflle and the drum outlet.

4. Pulverizing apparatus comprising a drum having an inlet and an outlet, means for introducing material to be pulverized into the drum, 9. classifier having an inlet connected to the outlet of'the drum, means for withdrawing pulverized material from the drum and through the classiof pulverized material therethrough, means tor 7 adjusting the baflie so as to vary the path oi. flow 76 of the pulverized material through the classifier, means for returning coarse material from the classifier to the drum disposed below the baflle, and a screen above said last mentioned means and disposed between the baiiie and the drum outlet.

5. Puiverizing apparatus comprising a drum having an inlet and an outlet, means for introducing material to be pulverized into the drum,

m a classifier having an inlet connected to the outlet ot the drum, means for withdrawing puiverized material from the drum and through the classifier, a battle in the classifier for directing the flow o! pulverized material therethrough,

means for returning coarse material from the classifier to the drum, and a screen at the bottom of the baille'and above said last mentioned means and disposed between the bailie and the drum outlet.

MARTIN FRISCH. 

